A guy I know did this in league one time, he was a very weak player btw, and I found it kinda funny. He noticed his opponent shooting the wrong balls, waited until his opponent ran all the balls and was on the 8-ball, then called a foul. Took ball in hand for a straight in shot on the 8.
I've also seen him keep shooting on obvious flukes.
Also one time, his opponent was on a break-and-run, just had to cut the 8 into the side. The cue ball would be tracking towards the corner, but there were a couple balls blocking the pocket, so there was almost no way to scratch. Somehow, the cue ball managed to hit off of those couple balls and just roll in the pocket. This guy jumps out of his chair and cheers with his fists in the air.
Anyway this guy isn't a bad guy really, he's just a very weak player that doesn't understand the etiquette of pool. He, as a person, reminds me a lot of George Costanza.